Bangladesh, July 8 -- The Pakistan Airports Authority said the privately operated freighter, operating as flight TA1732, lost contact with air traffic control after reporting problems with its navigation system. The Karachi Area Control Centre offered navigational assistance, but the aircraft soon began rapidly losing altitude while changing course.

The jet reported the issue at 9:18 pm and was cruising at 35,000 feet at roughly 442 knots. By 9:21 pm, it was seen "rapidly descending" with a sharp change in heading before radar and radio contact were lost about 287-300 kilometers west of Karachi.

Preliminary ADS-B data indicated a loss of altitude, followed by a climb, then a second, sudden loss of altitude. The final data point placed ...